Event Loop Visualizer
Finally understand JavaScript's event loop. Watch how setTimeout, Promises, async/await, and queueMicrotask interact with the call stack, microtask queue, and macrotask queue — in real-time.
What You'll See
Macrotask Queue
Watch setTimeout and setInterval callbacks queue up and execute after the current call stack clears.
Microtask Queue
See how Promise.then, queueMicrotask, and async/await callbacks execute before macrotasks.
The Full Loop
Understand the complete cycle: call stack → microtasks → render → macrotasks, and why order matters.
Why Is the Event Loop So Important?
The event loop is the heart of JavaScript's concurrency model. Every setTimeout, every fetch call, every DOM event handler goes through the event loop. Misunderstanding it leads to race conditions, UI freezes, and unpredictable async behavior.
The classic interview question “What does this code output?” almost always involves the event loop. With Code Visualizer's visualizer, you can paste any snippet and watch the execution order unfold — no more guessing.
Common Misconceptions
Many developers think setTimeout(fn, 0) runs immediately, or that async/await makes code synchronous. The event loop visualizer shows you exactly why these assumptions are wrong.